AC Circuits & Voltage

The actviphysics activity showed us that once current reaches a certain value, the emf is no longer induced. The current left is produced by the battery used. We also solved for current using the formula I=V/R and solved for the time constant. 

Below are graphs of voltage and current over time. The derivations for Vrms, Irms,  Imax, and Vmax are shown too. 

Here we set up our circuit board with a resistor known resistance. We connected the voltage probe across the source and set the frequency to 10Hz on the function generator connected. 

Our graph on logger pro was as shown. We used the peaks on graph to find the Vmax and Imax. 

The voltage vs current ended up being a linear graph. 

The linear fit graph is shown.

We then compared our experimental values with our theoretical values and found the percent error. 

Here is a derivation for current as a function of capacitance. Current is directly proportional to the frequency. 

The difference between AC circuits and DC circuits in regards to Ohm's Law is the value of Z, where Z represents impedance. The proportionality of current and voltage can be checked by testing for linearity in the current vs voltage graph.

Next we set up our function generator with a current probe in series with the capacitor. 

Our graphs for current vs time, voltage vs time, and voltage vs current are as shown. The peaks of voltage and current are different. We later used the difference in the peaks to determine the phase change. 

Below are calculations for Vrms, Irms, frequency, percent difference and phase change. 

Here are derivations for current and voltage in terms of inductance, omega, time, and theta.

Finally we experimented on the inductor, and connected our function generator across the inductor with a current probe in series with the inductor. 

We viewed the graphs using logger pro.

We performed the calculations for Vrms, Irms, impedance and percent difference. Our values were very different from the theoretical value. We noticed that lab groups around us had the same large percentage difference. This large difference could be due to miscalculations or the inductor used.  

Summary:

• An AC circuit is a circuit in which voltage and current vary sinusoidally with time.
• the average current and voltage on any AC circuit is zero because of the negative and positive values due to frequency
• In each cycle, voltage and current hit certain peaks that can be used to find the Vmax, Imax, Vrms and Irms. 
• In AC circuits obey Ohm's Law but have one important difference. The impedance is calculated differently.